At a Senate hearing yesterday, some proposals got their first formal airing. Others, such as a controversial suggestion to revise the attorney general's guidelines on surveillance, face further closed-door scrutiny.

In the nine days since the bombing, bold pronouncements have given way to more cautious assertions about enhancing federal crime-fighting ability. What's clear is that Congress will pass legislation. The challenge will be to strike a new balance between enhanced security and continued vigorous protection of individual rights.

But the bottom line, say experts on terrorism and law enforcement, is that no government can guarantees that a serious terrorist attack will never occur again.

''We face a test of the civil-rights tradition in this country,'' says John Shenefeld, chairman of the American Bar Association's working group on terrorism. ''Traditionally, we have managed with minimalist law enforcement; we're still far more relaxed than, say, the English, the Germans, the French. [But] we may be seeing a sea change in the way openness is seen.''

Indeed, public-opinion polls since the Oklahoma bombing show a heightened willingness by citizens to forgo civil liberties in an effort to avoid future tragedies.

This week the president proposed to Congress a series of measures aimed at enhancing law enforcement efforts to fight domestic terrorism. They include:

* Adding 1,000 new federal agents and prosecutors. This would represent a significant increase over the number involved in counterterrorism, officials say.

* Allowing federal law-enforcement officials to call in the military in cases involving weapons of mass destruction, such as biological and chemical weapons. This proposal alarms civil libertarians because it would amend the Posse Comitatus Act of 1878, which forbids military involvement in domestic crime cases.

The Oklahoma attack has also given new impetus to existing antiterrorism legislation. Civil-liberties and Arab-American groups have opposed that bill, because of a provision that would allow for easier deportation of ''suspected terrorists.''

''If this bill had already become law, we would have seen 10 or 12 Arabs or Muslims deported in the last week alone,'' without benefit of due process, says Khalil Jahshan, executive director of the National Association of Arab-Americans.

With all the proposed legislation, the administration and Congress are mindful of the lessons of history. In the 1960s and '70s, antiwar protesters, feminists, and other activist groups were subject to excessive investigation and surveillance, leading to the issuance of new law-enforcement guidelines. Those guidelines were relaxed in 1983 under the Reagan administration, opening the government to charges that it targeted groups it opposed on political grounds.

Congressional GOP leaders and the Clinton administration have been reminded repeatedly of the potential for civil-liberty abuses in enhancing law enforcement powers. On that issue, the administration says it will issue a presidential directive within the next 60 days. House Speaker Newt Gingrich (R) of Georgia has also proposed a congressional oversight committee to guard against abuses by law enforcement.

Phil Gutis, spokes-man for the American Civil Liberties Union (ACLU), says law-enforcement guidelines now allow agents to do all they need to do to investigate and infiltrate potentially violent groups. ''We doubt they can write new guidelines that would prevent investigation of groups that are simply not in favor, like the ACLU or the National Rifle Association,'' Mr. Gutis says.

Neil Livingstone, a terrorism expert, disagrees. ''It shouldn't be hard to draft guidelines that define what kinds of action or behavior would merit investigation before criminal action,'' he says. The key, he adds, is for the guidelines to be clear and to include adequate public accountability.

Mr. Shenefeld, also a former Justice Department official, suggests that fear of lawsuits may keep some agents from being more aggressive in investigating groups. ''[Agents] all claim it's a real factor in their decisionmaking,'' says Shenefeld, who notes some have faced personal bankruptcy after being sued.